Coasting economizer



Jan. 11, 1955 M. B. HEFTLER ETAL 2,699,157

COASTING ECONOMIZER Filed Dec. 50, 1950 2 Sheets-Sheet 1 25 FIG. I

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Jan. 11, 1955 M. B. HEFTLER ET AL 2,699,157

COASTING ECONOMIZER Filed Dec. 30, 1950 2 Sheets-Sheet 2 FIG.4

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l I I l l 400 800 I200 9 INVENTORS P 0% United States Patent COASTIN G ECONOMIZER Maurice Ben Heftler and Pierre Victor Heftler, Grosse Pointe Park, Mich.

Application December 30, 1950, Serial No. 203,614

6 Claims. (Cl. 123-119) The object of this invention is to provide a device to stop the flow of fuel from the carburetor whenever the engine is coasting, and to make the device small enough for easy installation, even where space is at a premium. We call this device a coasting economizer. Coasting here is defined as that engine operating condition where the speed of the engine is greater than it would eventually be with the clutch disengaged; in other words, the engine is overrunning its throttle position. This can happen in more than one way; an engine may be turning under its own momentum (vehicle in motion, throttle suddenly closed); or it may be driven by the load, absorbing energy from the load and acting as a brake (vehicle coasting down a hill in low gear with the clutch engaged).

No power is asked of the engine when it is coasting; any fuel then consumed is wasted. Normally, carburetors supply fuel even when the engine is coasting, but this is a defect in carburetors. This invention overcomes this defect.

This carburetor defect gives rise to many undesirable effects: The worst is a bad odor in the exhaust gas. Other undesirable results of supplying fuel during coast- 'ing include spark plug fouling, increased crank case dilution, increased cylinder and ring wear, and spitting and popping and even mild explosions in the exhaust manifold and mufller. Lastly, fuel is wasted.

All these undesirable effects can be avoided by shutting off the fuel whenever the engine is absorbing power, and by supplying fuel only when power output is required. Previous devices for this purpose have been responsive to inlet manifold vacuum, but this alone is not a proper indicator to distinguish coasting conditions from power delivery: At zero load the manifold vacuum is not a constant at all speeds; it peaks at about 1200 revolutions per minute, and is considerably less at lower and at higher speeds. In this invention, the coasting economizer is responsive to two vacuum forces, their difference at zero load being substantially constant up to about 1200 R. P. M.

Previous devices have had considerable hysteresis in their mechanisms, and they have had a relatively low sensitivity. Our invention offers means of substantially eliminating hysteresis and of increasing sensitivity to whatever value may be desired.

Figure 1 shows the coasting economizer connected to a carburetor.

Figure 2 shows an alternate connection.

Figure 3 is a scale drawing of a commercial form of the invention.

Figure 4 is a section of the diaphragm used in Figure 3, shown at rest.

Figure 5 is the same diaphragm as Figure 4, in the shape it assumes when the pressure is lower on one side than on the other.

Figure 6 shows a further variation in diaphragm design.

Figure 7 and Figure 8 show two forms of coasting economizer with a variable controlling vacuum.

Figure 9 is a graph of certain engine variables.

In our invention the fuel is shut off by bleeding air into a fuel channel, normally under vacuum, thereby raising the pressure in the channel to the point where fuel is no longer sucked into the channel. Now, carburetor fuel channels convey either liquid fuel or an emulsion of fuel and air; accordingly, in Figure 1 the coasting econ- "ice omizer bleeds air into an emulsion channel; and in Figure 2 it bleeds air into a liquid fuel channel.

Referring to Figures 1 and 2, the main fuel nozzle 1 is here shown discharging into the throat of a secondary venturi. The throttle plate 2 is shown in the idle, or closed position. The lower priming hole 3 is on the high vacuum side of the throttle plate. The upper priming hole 4 is on the low vacuum side of the throttle when it is closed, but it transfers to the high vacuum side as the throttle is opened. The volume of flow through the lower hole 3 is adjusted by the screw 5. Channel 6 supplies the priming holes 3 and 4 with air and fuel sucked in from the air bleed 7 and from the idle jet 8. The idle jet 8 gets fuel from the bowl from below the liquid level, LL.

In some carburetors the priming holes 3 and 4 are replaced by a slot and the adjustment screw 5 acts on the air bleed 7. What takes place in channel 6 is the same in either case, and the invention is equally applicable to both systems.

With the throttle plate closed, a relatively low vacuum exists in channel 6. Fuel enters channel 6 through jet 8. Air enters through air bleed 7 and the upper priming hole 4. The only exit from channel 6 is the lower priming hole 3.

As the throttle plate is opened the upper priming hole 4 becomes obstructed by the throttle plate 2 and its passage of air is reduced, thus increasing the vacuum in channel 6. As the plate is opened beyond that point, the upper hole 4 is exposed to the high vacuum existing below the plate and it then passes air and fuel from channel 6 into the main air stream, in parallel with the lower priming hole 3, thus further increasing the vacuum in channel 6.

In Figure l, the coasting economizer 9 has the full area of one side of its diaphragm 10 exposed to the vacuum existing below the throttle plate 2, brought to it through channel 11. The vacuum force is resisted by the spring 12, which may be adjusted by the screw 13, and by the vacuum existing in channel 6 and conveyed through channel 16 applied over a portion of the other side of the diaphragm 10 by the area of the seat 14.

Whenever the vacuum in channel 11, working on the effective area of the diaphragm, exerts a greater force than that of the spring plus the force due to the vacuum in channel 6, acting on a portion of the diaphragm, the diaphragm lifts from its seat and passes air from channel 15 into channel 16, thus relieving the vacuum in channel 6 and reducing the flow of fuel through jet 8. When enough air is passed the vacuum in channel 6 is reduced to the threshold value of jet 8 and fuel flow stops completely.

The area of the diaphragm acted on by the vacuum in channel 6 is adjusted, in design and manufacture, to best meet the requirements of a given engine and carburetor, so as to be just sufiicient to prevent opening of the diaphragm on the normal increase in manifold vacuum above idle vacuum occurring at no load with slight throttle openings. Although the vacuum in channel 6 is very low at idle (one inch of mercury, or less), it increases rapidly on throttle opening to as much as 14 inches of mercury. Even so, a substantial area of the diaphragm must be utilized to prevent false operation. Typical values for the area of seat 14 are from one quarter to one-half the total diaphragm effective area.

In Figure 2, the coasting economizer 9 is connected to bleed air into the liquid side of jet 8 through channel A much smaller air flow is sufficient to stop fuel flow than in the arrangement of Figure 1. The vacuum existing in channel 16a is less than that in channel 6, so the area of seat 14 must be considerably greater at no-load speeds under 1500 R. P. M. The main jet does not usually flow fuel during coasting conditions, but when it does a coasting eeonomizer can be connected into it, as well as one into the idle system.

A very considerable problem in devices of this sort is to achieve adequate sensitivity in the diaphragm, without hysteresis, in order to require as little change in manifold vacuum as possible for full operation of the device. This problem is not solved by using a spring with a very low rate of force increase with displacement, or by using gravity in place of a spring, or by using a very large diaphragm, because conventional diaphragms themselves inherently have a rate of force decrease with displacement; furthermore, they exhibit hysteresis, especially if made of rubber or the like.

First, consider the rate inherent in a conventional diaphragm: Diaphragms flex under the influence of the pressure difference on opposite faces. A portion of the force acting on the diaphragm is transmitted to the periphery of the diaphragm by which it is held in place, and a portion is transmitted to the center of the diaphragm which moves to do work; the relative proportions transmitted to the periphery and to the center depend on the position of the diaphragm. The proportion transmitted to the center is greatest when the stroke is at minimum, as when there is minimum pressure difference across the diaphragm. As the diaphragm is allowed to move, as by an increase in pressure difference, the proportion transmitted to the center decreases; consequently the diaphragm effective area decreases with displacement. With a given pressure difference the force generated across the diaphragm changes with its position and the effect is that of a stiff spring.

As to the hysteresis, we observe that conventional diaphragms made of elastic materials are of fairly uniform thickness throughout. The thickness at the central clamp and the thickness at the peripheral clamp are both about the same as the thickness in the flexing portion. As the pressure difference that operates the diaphragm changes, more or less of the diaphragm material is pulled in and out of the clamping means. This motion is accompanied by friction. which results in hysteresis. The displacement of the diaphragm is not the same for increasing pressure differences as it is for decreasing pressure differences.

In this invention, we show a diaphragm structure that is virtually free of hysteresis, a structure that has a very small change in effective area, and, in one variation. a structure that has a negative change in effective area, which improvements contribute to the success of the coasting economizer. It must be exceedingly sensitive, and it must be free of hysteresis, if it is to have any utility.

In Figure 3, which is a half section scale drawing of a commercial coasting cconomizer. the parts not ideuti fied in Figures 1 and 2 are as follows: 17 is the outer rim of the diaphragm and is used to hold the diaphragm in place: 18 is the center of the diaphragm, the part that moves in response to changes in pressure difference; 19 is a thin connecting web between the center 18 and the rim 17; and 21 is a plate which serves to support the center of the diaphragm and to keep it fiat. 21a is a stop to prevent excessive diaphragm travel. Spring seat 22 transmits the spring load to the dia hragm through plate 21. The connection from the spring se t 22 to the diaphragm plate 21 is by the spherical end 23 of the spring seat bearing in the conical socket 24 of the diaphragm plate; this construction has been found desirable in order to avoid any tendency of the sprin which may bear with more force on one side than on the other under load, to exert an eccentric loading on the diaphragm, which would prevent the diaphragm center 18 from remaining parallel to the seat 14 when it is bein lifted from the seat by the vacuum forces. The conical socket 24 is placed well below the plane of the diaphragm web 19 so as to lessen the effect of eccentri ity of the socket in relation to the diaphragm web. The effect of this entire arrangement is to give a dia hragm center 18 suspended between two opposing forces in such a way as to be free to float: between them without being cocked by either of them; thereby it is possible to achieve the maximum sensitivity and to transform that sensitivity into maximum valve opening.

Figures 4, 5, and 6 are sectional views through circular diaphragms that are virtually free Of hysteresis.

They are preferably molded out of synthetic rubber, or some other homogeneous elastomer. The outer rim 17 is gripped in the diaphragm holder. The inner section 18 may be gripped by the center structure that the diaphragm is to move, or it may simply bear against a plate 21 between it and the spring. The web 19, which con nects the periphery 17 to the center 18, is made very much thinner than the rest of the diaphragm, and it is the only portion of the diaphragm to change its shape appreciably during changes in actuating pressure or displacement.

Figure 4 shows the diaphragm in the at rest, or as molded, position. Figure 5 shows the deformation of the web occurring in response to a pressure difference. All of the material in the web 19 is working in tension. The thickness of the web material is designed for the pressure difference that is to be encountered and for the elastic properties of the material so that the radial elongation of the material is in the order of 10%. This gives an arc of curvature of the web of about 60 from a flat molded web, and this is sufficient to make the change in effective area of the diaphragm with displacement a very small proportion of the effective area.

If the resultant change of diaphragm force with displacement is too great for a given application. the structure shown in Figure 6 may be used. In this case the web 20 is molded with a curvature so that it has the shape of a section of a torus. If the section, under the influence of the pressure difference, has an included are of more than the effective area of the diaphragm will increase with displacement in the direction of low pressure. Thus this type of diaphragm has a negative rate. It may be made as sensitive as desired by combination with the positive rate of a suitable spring.

These diaphragms are all substantially free of hysteresis because the only portions that change shape appreciably under load are the webs 19 or 20. The rest of the diaphragm is four times or more as thick as the web, and the load carried from the web to the center 18 and to the periphery 17 is spread out over four or more times as much material, resulting in elastic displacement only, without sliding of these parts on supporting structures, and therefore without friction and hysteresis due to friction. There only remains the internal hysteresis in the diaphragm material itself, and this exerts but a negligible influence on the motion of the diaphragm for a reason which will now be explained: Hysteresis in the elongation of the web has substantially no effect on the motion of the diaphragm center if two conditions are met: First, the web must be very thin, otherwise its curvature may, in itself, generate small bending movements which can introduce hysteresis: Secondly, the travel of the diaphragm center must not be so great as to bring the outer or inner edges of the web into tangency with a plane parallel with either the plane of the outer rim 17 or the plane of the center 18; in other words, and lo king at Figure 5. the ballooning of the web induced by the pressure difference should always reach a maximum somewhere near the middle of the web and not at its inner or outer edge, otherwise, the web itself will act as a tension member between the center part and the outer rim of the diaphragm and in that case the diaphragm will have hysteresis if the web material has hysteresis in elongation. In this invention we have found that synthetic rubber diaphragms of 54 durometer hardness or softer, with webs .060 inch wide and .010 inch thick have ample travel of the diaphragm center, with no evidence of hysteresis.

In case the diaphragm of Figure 6 proves too difficult to manufacture and in case the diaphragm of Figure 5 is not sufficiently sensitive, the over-all action may be made as sensitive as desired by using one of the constructions shown in Figure 7 and Figure 8, in which a portion of the manifold vacuum is applied to the spring side of the diaphragm through channel 11, and in which that portion increases with diaphragm displacement.

In Figure 7, manifold vacuum from channel ll is admitted to the spring chamber through orifice 25, which is partially obstructed by the needle 26, having a conical portion in the orifice and being attached to the diaphragm. Air is admitted to the spring chamber through the leak hole 27.

In Figure 8, manifold vacuum from channel 11 is admitted to the spring chamber through the fixed orifice 28. Air is admitted through orifice 29 which is partially obstructed by the needle 30 attached to the diaphragm.

In both Figures 7 and 8, the vacuum on the spring side of the diaphragm is less than manifold vacuum, but it increases with diaphragm travel because of the taper in the needle, 26 or 30, as the case may be. The degree of taper and the sizes of the inlet and outlet orifices may be adjusted in design and manufacture so as to give Whatever degree of vacuum increase with displacement may be required to overcome the rate of the spring and the reduction in effective diaphragm area that occurs with displacement. The coasting economizer may thereby be made as sensitive as desired.

Now we consider the nature of the vacuum forces in a carburetor, and which are to be used to actuate this device. In Figure 9, we show curves of manifold and fuel system vacuum existing at different engine speeds, all without load on the engine; these curves explain the necessity of introducing a significant portion of fuel systern vacuum in opposition to manifold vacuum so as to obtain a discrimination between load conditions and coasting conditions that is substantially independent of speed. M is the curve of manifold vacuum existing in channel 11. I is the curve of fuel system vacuum existing in channel 6. It will be noticed that M increases with speed up to 1200 R. P. M., and subsequently decreases.

Since manifold vacuum (curve M of Fig. 9) is not constant at zero load, it cannot serve as an accurate indication of load. It alone cannot tell with precision when the engine is coasting and needs no fuel. Previous de vices for shutting Off the fuel during coasting have been responsive to increase in manifold vacuum: they have used curve M alone. These previous devices had to be adjusted so as to open only when the peak of curve M was exceeded. They could be quite sensitive in the region of the speed that gives the peak no-load manifold vacuum, neglecting hysteresis and a high spring and diaphragm rate. But at speeds below this peak the throttle would have to be closed considerably in order to develop a manifold vacuum exceeding the peak; and at speeds below about 800 R. P. M., operation of previous devices would not occur because sufficient vacuum could not be developed even if the throttle were entirely closed. As a result, previous devices functioned only during severe coasting conditions, only when the throttle was closed virtually all the way at speeds exceeding 800 R. P. M.

Again referring to Figure 9, fuel system vacuum, curve I, also increases with speed, at zero load, but it increases much more rapidly than does curve M. If we were to construct a new curve F equal to curve M minus X% of curve I, we could make this new curve F fairly level over a wide speed range, and new curve F would be a more accurate indication of load independent of speed. This very important part of the invention is effected as follows:

In this invention, we apply the manifold vacuum M to one side of the diaphragm 10 over its entire area. We oppose the force it develops with a spring 12 and with fuel system vacuum (curve I) applied to the opposite side of the diaphragm over a substantial portion of its area by seat 14. In Figure 3, the area of the seat is one third as great as the area over which manifold vacuum is effective.

The net resulting vacuum forces on the diaphragm are shown as curve F, for the no load condition which is the dividing line between power delivery and power absorption by the engine. This curve is nearly straight, and it can be made almost level, up to the speed that gives the peak manifold vacuum, by making the area of seat 14- just right for a given engine and carburetor. This curve discriminates nicely between engine conditions that require fuel and engine conditions that waste fuel. It is a far better discriminator than manifold vacuum alone. The spring 12 can be adjusted so as to just hold the diaphragm on its seat at no load for all speeds up to about 1200 R. P. M. It is set to balance curve F.

The operating cycle of the device is as follows: If coasting occurs due to closing the throttle, manifold vacuum increases, fuel system vacuum decreases, and the net vacuum force on the diaphragm increases considerably, overcoming the spring and causing the valve to open and bleed air into the fuel system. This further reduces the fuel system vacuum and further increases the force on the diaphragm. The air bled into the fuel system, if bled in sufficient volume, stops the flow of fuel. When the engine has decelerated to the speed corresponding to the new throttle position, or to one slightly below it, the vacuum forces have become weaker than the spring and the valve closes, reestablishing normal carburetor operation.

Similarly, if coasting occurs due to overdriving the engine by the load, manifold vacuum increases, fuel system vacuum increases very slightly, and the net vacuum force on the diaphragm increases, opening the valve and stopping the flow of fuel. When coasting ceases by an opening of the throttle or by removing the overdriving force on the engine, manifold vacuum drops and the valve starts to close. As soon as the valve restricts the air bleed into the fuel system, the increase in fuel system vacuum accelerates the closure of the valve.

If fuel system vacuum, one of the operating forces on the diaphragm, were allowed to drop to zero by a full opening of the valve, this would introduce a trigger action, increasing the differential between valve opening and valve closing conditions. This is prevented by limiting the opening of the valve to an amount that drops the vacuum in the fuel system to below that required to draw fuel, but not to zero. Valve stroke is limited by a stamping 21a, in the commercial form of this invention. With the spring set to close the valve whenever the engine speed drops to that corresponding to the throttle position, valve opening occurs on a speed increase of only R. P. M. or on a closure of the throttle corresponding to a speed decrease of only 100 R. P. M. This fine sensitivity is the result of the several features disclosed in this invention, including utilizing two vacuum forces suitably proportioned and opposed for operation, eliminating friction and hysteresis in the diaphragm, and avoiding an adverse change in effective diaphragm area with displacement, all of which are necessary for successful operation. 1

We claim:

1. A device for deactivating the fuel system of the carburetor of an engine whenever the engine is coasting, including a housing, a flexible diaphragm within said housing and dividing the same into two chambers, a tube extending into the first of said chambers and terminating in an open end, said end being at and in the plane of said diaphragm, adjustable elastic means urging said diaphragm into closed position against said open end of said tube, and pneumatic connections between said device and the carburetor as follows: a passage connecting the other end of said tube to the fuel system of the carburetor, a passage connecting the first chamber to the air inlet of the carburetor, and a passage connecting the other chamber to the manifold outlet of the carburetor and maintaining said other chamber substantially at manifold vacuum.

2. The structure defined in claim 1 wherein the ratio between the area of the open end of said tube and the area of said diaphragm is approximately the same as the ratio of: (a) the excess of the maximum zero load manifold vacuum over manifold vacuum at idle, to (b) the excess of fuel system vacuum at the speed where Zero load manifold vacuum is maximum over fuel system vacuum at idle speed.

3. The method of determining, over a given speed range and from conditions within the carburetor, when a gasoline engine is overriding the throttle position of the carburetor, consisting of measuring the difference between (a) the induction vacuum in the outlet of the carburetor, and (b) the vacuum in a carburetor fuel channel times a constant; the constant being substantially equal to the increase in induction vacuum divided by the increase in fuel channel vacuum when the engine is operated at no load from the beginning to the end of said given speed range.

4. A valve for reactivating the fuel flow of a gasoline engine carburetor whenever, over a given speed range, the engine is overriding the throttle position of a said carburetor, the characteristics of the engine-carburetor combination being such that, over the aforesaid speed range and the engine at no load, there is as the throttle is opened a progressive increase in manifold vacuum and a progressive increase in the vacuum in a fuel channel of said carburetor, said valve including a moveable member having one surface subject to said manifold vacuum and urging movement of said member in a given direction and a second surface subject to the vacuum in said fuel channel and opposing said movement, the relative areas of said first and second surfaces being proportioned so that the said progressive increase in vacuum applied to said second surface from said fuel channel offsets said progressive increase in the manifold vacuum applied to said first surface as the throttle is opened over the aforesaid speed range with the engine at no load.

5. A device for deactivating the fuel flow of a gasoline engine carburetor whenever the engine is overriding the throttle position of said carburetor within a given speed range, said device including valve means responsive to (a) the manifold vacuum of said engine, and (b) the vacuum in a carburetor fuel channel multiplied by a constant, said constant being substantially equal to the increase in manifold vacuum divided by the increase in fuel channel vacuum when the engine is operated at no load from the beginning to the end of said given speed range, said valve means having one surface subject to said manifold vacuum and a second surface subject to said fuel channel vacuum, the relative areas between said first and second surfaces being substantially equal to said constant.

6. A fuel fiow regulating device for use with a carburetor having an idle mixture system for decreasing the ratio of the fuel-air mixture developed by said carburetor to substantially zero under conditions where the engine is coasting; said device comprising an air passage communicating at one end with the idle mixture system of said carburetor, valve means normally closing said air passage and being responsive to the pressure differential between manifold vacuum and idle fuel system vacuum times a constant, said constant being substantially equal to the increase in manifold vacuum divided by the increase in fuel system vacuum when the engine is operated at no load from the beginning to end of a given speed range, said valve means including a first surface and a second surface, means for subjecting said first surface to manifold vacuum, means for subjecting said second surface to fuel system vacuum, the ratio between the areas of said first and second surfaces being substantially equal to said constant, and adjustable means resiliently opposing opening movement of said valve means for establishing a minimum pressure differential for opening movement.

References Cited in the file of this patent UNITED STATES PATENTS 2,036,205 Ericson Apr. 7, 1936 2,094,555 Von Hilvety Sept. 28, 1937 2,367,499 Holley, Jr. Jan. 16, 1945 2,391,755 Twyman Dec. 25, 1945 FORElGN PATENTS 405,346 Great Britain Feb. 8, 1934 

